Portable collapsible scaffold



OC- 14, 1969 cm L. ATCHEY 3,472,337

PORTABLE COLLAPSIBLE SCAFFOLD u Filed Oct. 27, 1967 3 Sheets-Sheet A /50M@ 72a 5e /50 /56 a 92 IE 1 E.- E

INvErJTOR Genesi- L, rcHf-Y United States Patent O 3,472,337 PORTABLECOLLAPSIBLE SCAFFOLD George L. Atchey, Midwest City, Okla., assignor toVePed Traffic Controls, Inc., Oklahoma City, Okla., a corporation ofOklahoma Filed Oct. 27, 1967, Ser. No. 678,734 Int. Cl. E04g 1/00; E06c5/06; A01g 19/04 U.S. Cl. 182-2 11 `Claims ABSTRACT OF THE DISCLOSURE Ascaffold apparatus which can be demountably positioned in the bed of atruck, and while so positioned, can be expanded to an elevated status,or which can be similarly expanded when demounted and rested on theground. The structure includes a horizontal base structure having a pairof substantially parallel boom elements, each pivotally secured at oneend to one end portion of the base structure, and secured at theiropposite ends to a substantially horizontally extending work platform. Apiston and cylinder structure interconnected between the base structureand one of the booms provides power for elevating the booms and workplatform. Sockets are provided on the base structure to receive theupper ends of a plurality of Outrigger jack structures, which whenplaced in the sockets, extend to the outside of a truck in which thescaffold apparatus is mounted and into contact with the ground. TheOutrigger jacks can then be used for manually off-loading the scaffoldapparatus to the ground.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to expandable work platforms and scaffolding which can be usedto elevate a workman to a high work location, or folded down to acompact, inoperative status. More particularly, the invention relates toexpandable scaffolding of the type which can be transported and usedwhile mounted upon a light truck.

Brief description of the prior art A number of instances exist where itis necessary to elevate a workman above ground level in an outdoorlocation for the purpose of permitting the workman to make relativelyrapid repairs to elevated structures, such as street lights, trolleypower lines, traffic signal lamps, and the like. For this purpose, anumber of special vehicles have heretofore been built which incorporatea rather massive scaffolding structure which can be elevated to selectedheights, can be swiveled about so as to move the workman in a horizontaldirection, and can be driven from one location to another. Many of thesestructures contain complicated machinery and are relatively expensive toconstruct and maintain. In most instances, the scaffolding or structureemployed to elevate the workman cannot be easily detached or demountedfrom the framework of the vehicle, but rather, is made a permanentportion of the vehicle, thus rendering the vehicle incapable of otherutility, and requiring that both the vehicle and scaffolding structurealways be present at the same location. In other instances, equipment ofthe general type described has been so large in its vertical dimensionthat freedom of movement of the vehicle is some- 3,472,337 Patented Oct.14, 1969 ice what restricted, and care must be exercised in traversingunderpasses and tunnels having a limited vertical clearance.

Although applicant is aware of one prior proposal to demountablyposition an elevatable work platform on a truck, such as is depicted anddescribed in U.S. Patent 3,283,850, this assembly does not provide anyrapid and easy method for detaching the structure from the vehicle andmanually lowering it to the ground.

BRIEF DESCRIPTION OF THE PRESENT INVENTION The present inventionprovides a portable collapsible scaffold which can be utilized toelevate a workman to a substantial height, either when the scaold issupported on the ground, or when it is mounted in quick detachablefashion on a relatively small, lightweight truck. The scaffold can beeasily mounted on, or demounted from, a truck by a single operator, sothat the entire assembly, including the truck and collapsible scaffold,can be operated by a single workman. The portable collapsible scaffoldcarries a self-contained power unit which permits it to be operatedindependently of the power plant of the truck. Moreover, when thescaffolding is folded downwardly to its collapsed or traveling position,it adds very little to the total height of the truck and consequentlyproblems of inability to pass beneath relatively low ver tical clearancestructures are seldom encountered.

Broadly described, the present invention comprises a base structurewhich is adapted to be secured to the bed of a truck and having aforward end portion and a rear end portion; a pair of substantiallyparallel, elongated boom elements each pivotally secured at one end tothe rear end portions of the base structure at horizontally spacedlocations for pivotation about spaced, substantially parallel,horizontal axes; a horizontally extending work platform secured to theends of said booms opposite their ends pivotally secured to said basestructure; and an extensible piston and cylinder means connected betweensaid base structure and at least one of the booms to provide power forsimultaneously elevating the booms by pivotation about said horizontalaxes. A first pair of forward sockets are secured to opposite sides ofthe forward end portion of the base structure, and a second pair ofsockets is secured to the base structure on opposite sides thereof andspaced rearwardly from the forward sockets. Outrigger jacks are providedwhich are engageable with the sockets secured to the base structure, andwhich each include a ground-contacting lower portion, and asocketentering upper portion which is horizontally offset from theground-contacting lower portion.

In a preferred embodiment of the invention, the base structure is madewith a pair of horizontally spaced parallel runners adapted to supportthe base structure on the flat bed of a truck, and having a plurality ofsecuring plates connected to the runners to permit the portable scaffoldstructure to be secured to the truck bed by bolts. The Outrigger jacksare manually operable so that when they are engaged with the socketsprovided on the base structure, a four-point support for the scaffoldstructure is provided, the scaffold can be elevated manually, and thetruck driven out from under the scaffold to permit it to be demountedfrom the vehicle and lowered to the ground. A further important featureof a preferred em- Y N"at-Ellapserfrinoperatiue`p`osition.

the two booms which are provided in the scaffold structure, whichnesting arrangement permits the booms to be pivoted downwardly abouttheir horizontal pivotal axes until both extend horizontally insubstantially the same plane. This permits the scaffold structure tooccupy a minimum vertical dimension in its folded down or collapsedstatus, so that the vehicle on which it is mounted encounters nodifficulty in traversing underpasses, tunnels, and the like.

From the foregoing general description of the invention, it will havebecome apparent that a major and important object of the invention is toprovide an improved, portable, collapsible scaffold which can be easilymounted on, or demounted from, a lightweight truck so that the truck canbe utilized for servicing and maintaining vertically elevatedstructures, and can also be used at other times in the normal fashioncharacteristic of lightweight trucks without impairment by the presenceof the scaffolding.

An additional object of the invention is to provide a vehicle carryingelevatable scaffolding to permit a work man to be elevated to a highvertical level, which scaffolding can be folded down to a compactposition in which the vertical dimension of the entire structure is onlyslightly greater than the distance from the ground to the top of the cabof the vehicle.

An additional object of the invention is to provide a portablecollapsible scaffold which includes a selfcontained power plant, andwhich can be used either when mounted on a transporting vehicle or whenrested upon the ground.

An additional object of the invention is to provide a portablecollapsible scaffold structure which can be used with a maximum degreeof safety by a workman who is elevated by the scaffold structure.

A further object of the invention is to provide a portable collapsiblescaifold which automatically locks in a collapsed, compact, inoperativeposition.

Another object of the invention is to provide a portable collapsiblescalfold structure which can be quickly and easily disassembled if it isdesired to separately transport various portions of the structure fromone location to the other, or to repair or replace various portions ofthe structure.

Another object of the invention is to provide a portable scaffoldstructure having a self-contained power plant, with such scaffoldstructure including manual jack elements which permit the scaffoldstructure to be loaded and off-loaded on a vehicle for purposes oftransport, with such loading or off-loading being accomplished by asingle person.

Another object of the invention is to provide a portable collapsiblescaffold structure which is relatively inexpensive in construction, yetis of strong, durable character and possessed of a long and trouble-freeoperating life.

In addition to the foregoing described objects and advantages,additional objects and advantages will become apparent as the followingdetailed description of the invention is read in conjunction with theaccompanying drawings which illustrate the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a view in elevation of theportable collapsible scaffold of the present invention as the scaffoldappears when mounted on a pickup truck in its transport or collapsedstatus.

FIGURE 2 is a view similar to FIGURE 1, but showing the scaffold in itselevated operative status.

FIGURE 3 is a view in elevation from the rear of a pickup truck in whichthe portable collapsible scaffold of the present invention is mounted,and showing the scaffold in its expanded or elevated status. Guardfences ernployed in connection with the work platform of the scaffoldare shown in dashed lines to better illustrate the manner in which theseguard fences are folded down t FIGURE 4 is a view in elevation from therear of the pickup truck with the scaffold folded down to its collapsedposition, and illustrating outrigger jacks positioned and connected foroff-loading the scaffold from the truck.

FIGURE 5 depicts the portable collapsible scaffold of the invention asit appears after it has been off-loaded from the truck and placed uponthe ground with the scaffold collapsed to a compact, inoperative status.

FIGURE 6 is a plan view of the work platform ernployed in the scaffoldof the invention.

FIGURE 7 is a sectional view taken along line 7--7 of FIGURE l andillustrating the manner in which the power plant used to elevate thescaffold is mounted upon the base structure thereof.

FIGURE 8 is an enlarged detail view of a section taken along line 8-8 ofFIGURE 7.

FIGURE 9 is a schematic illustration of the engine, hydraulic pump, andhydraulic piston and cylinder assembly utilized in one embodiment of theinvention.

BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION In thefollowing description, reference will be made to various portions of theaccompanying drawings, with reference numerals associated with leadlines which have arrowheads being utilized to designate broadcombinations which include several subassemblies or several elementshaving a unitary function in the overall operation of the scaffold ofthe invention. Numerals which are connected to various structural partsby plain lead lines (having no arrowheads) will be utilized to designateindividual elements of structure.

Referring initially to FIGURE l of the drawings, a vehicle, typically apickup truck 10, is shown supporting the portable collapsible scaffoldof the present invention, designated generally by reference numeral 12.It should be understood, however, that one of the inventive aspects ofthe present disclosure is considered to be the structural combination ofthe portable collapsible scaffold with a vehicle of the type depicted,due to the novel and peculiar adaptability of the scaffold to the bedstructure of the typical pickup truck. Thus, the truck 10 includes theusual flat, substantially horizontally extending bed 14 located to therear of the truck cab 16 and having sideboards or side walls 18. Atailgate 20 is usually provided to provide a closure or gate extendingacross the rear of the bed 16 of the truck 10.

The portable collapsible scaffold 12 includes a base structure 22comprising a pair of substantially parallel, horizontally spaced,horizontally extending runners 24 (see FIGURES 5 and 7), and foursubstantially parallel, vertically extending corner posts, with the rearcorner posts being designated by reference numeral 26 and the forwardcorner posts being designated by reference numeral 28. The corner posts26 and 28 are each secured at their lower ends to the runners 24, andthe forward corner posts 28 extend to a slightly greater height than therear corner posts 26 for a reason hereinafter to be described. A pair ofcentral, vertically extending posts 30 are also provided in the basestructure 22 and are secured at their lower ends to the runners 24. Atransverse frame member 32 interconnects the rear ends of the tworunners 24, and a second transverse frame member 34 is secured betweenthe forward ends of the runners.

A central transverse frame member 36 extends between central portions ofthe runners 24 at about the location therealong where the lower ends ofthe central, vertically extending posts 30 are connected to the runners.For purposes of reinforcement, a purality of short diagonal braces 38extend across the corners between the runners 24 and the transverseframe members 34 and 36 (see FIGURES 3, 7 and 8), and a plurality oflong diagonal braces 40 are extended between the vertical posts 26, 28and 30 in the manner depicted in FIGURES 1, 2 and 3. Extending betweenand interconnecting the upper end portions of the vertical posts 26 isan upper transverse member 42 (see FIGURES 3 and 4), and a similar uppertransverse member (not visible in the drawings) interconnects thevertically extending posts 30. A transverse boom supporting bar 44extends between the forward, vertically extending posts 28, and issecured to these posts at points spaced downwardly a short distance fromtheir upper ends.

Secured to the outside of each of the forward, vertically extendingposts 28 at locations spaced downwardly a short distance from the upperends thereof are a pair of sockets 46 which, in the embodiment yof theinvention illustrated, take the form of open ended sleeves (see FIGURES2 and 7). Substantially identical sockets 48 are secured on the outsideof the rear, vertically extending posts 26 at positions spaceddownwardly from the upper ends thereof and at substantially the samelevel as the transverse member 42. The function of the sockets 46 and`48 will be subsequently explained in greater detail. A pair of stepplates 50 are secured to the inner sides of the rear, verticallyextending posts 26 at substantially the midportions thereof.

Mounted upon the base structure 22 of the portable collapsible scaifold12 are a pair of elongated booms, hereinafter termed an outer boom 52'and an inner boom S3. The terms outer and inner are utilized indescribing these booms because of the nested relationship of the boomswhen they are in their collapsed or inoperative positions as hereinafterfurther explained. The -outer boom 52 includes a plurality of elongated,longitudinal members 54 which are interconnected by transverse anddiagonal brace members 56 and 58, respectively. A plurality ofhorizontally extending transverse members 60 (see FIGURE 3) extendbetween the two uppermost longitudinal members 52 of the boom andsupport a ladder designated generally by reference numeral 62 and havingrungs 63 as depicted in FIGURE 3. The ladder 62 provides access to awork platform 64 which extends horizontally and interconnects two endsof the booms 52 and 53 as hereinafter explained. One end of the boom 52is pivotally connected to the base structure 22, and specilically to theupper end portions of the rear corner posts 26 by means of a pivot bar70, which pivot bar is journaled in a pair of pillow blocks 72 formed atthe upper end of each of the corner posts 26. The pillow blocks 72 areformed so that the upper portion 72a thereof, defining approximately 180'of the bore through the block which journals the pivot bar 70, can beremoved by loosening appropriate screws or bolts employed therewith,thus permitting the boom 52 to be completely disengaged from the upperportions of the rear corner posts 26. It will be noted that the upperportion 72a of each pillow block carries a suitable grease fitting 72b(see FIGURE 5).

The boom 53 is constructed generally similarly to the boom 52 and thusincludes transverse braces 80, diagonal braces 82 and transverse,horizontally extending members 84 (see FIGURE 3). It will be noted inreferring to FIGURES 2 and 3 that the horizontal spacing between thepairs of longitudinal members 78 of the boom 53 is less than thehorizontal spacing between the corresponding longitudinal members 54 ofthe boom 52 so that the boom 53 can fit within, or be nested inside of,the boom 52 when the two booms are pivoetd downwardly to the positiondepicted in FIGURE 1. It will further be noted that one end of the boom53 is connected in the manner hereinafter described to the work platform54, while the opposite end of this boom is pivotally connected to thebase structure 22. Connection of the boom 53 to the base structure 22 isaccomplished by the use of a pivot bar 90 to which the boom is securedand which extends through a pair of pillow blocks 92 secured to theupper ends of the central posts 30. The pillow blocks 92 are segmentallyconstructed similarly to the pillow blocks 72 hereinbefore described,and this construction permits the boom 53 to be detached from the basestructure 22 and removed from the assembly when desired.

The Work platform 64 includes a rectangular base frame 92 which has apair of heavy longitudinal boom attaching beams 92h positioned inwardlyof the frame and connected by a pair of transverse rods 92C. Therectangular base frame 92 and the beams 92b and transverse rods 92e`support an expanded metal oor grille 94. Each of the beams 92b carriesat a central position along its length, a hold-down clamp assembly 96which functions in a manner hereinafter described. Each holddown clampassembly 96 includes a tubular sleeve 96a which is welded to therespective beam 92h and slidingly receives a smooth bolt 96b. The bolt9617 carries a locking toe 96C at its upper end, and a cotter key 96d atits lower end. A helical springs 96e is interposed between the key 96dand the sleeve 96a.

Pivotally connected to the base frame 92 of the work platform 64 are aplurality of guard fences. In the embodiment of the invention depictedin the accompanying drawings, the guard fences include a forwardtransverse guard fence 98, and a pair of side guard fences 100 and 102(see FIGURES 2, 3 and 6). The guard fences 98, 100 and 102 are pivotallysecured to ears or lugs extending upwardly from the base frame 92 of thework platform 64, and such lugs are arranged in a manner such that thetwo side guard fences 100 and 102 can lbe pivoted downwardly abouthorizontal axes and in the manner illustrated by the dashed lines inFIGURE 3 as can the guard fence 98.

When all of the guard fences 98, ll00 and 102 are pivoted downwardly toa horizontal collapsed and cornpact position, they appear as shown inFIGURE 4, with the side guard fences 100 and 102 lying adjacent the baseframe of the work platform 64 with the forward transverse guard fence 9Scollapsed on top of the side guard fences 100, 102. The hold-down clampassemblies 96 are used to retain the guard fences in this collapsedposition by grasping the locking toes 96C, pulling the bolts 96hupwardly against the bias of the springs 96e, and pivoting the boltsabout their longitudinal axes so that the locking toes extend across andengage the top rail of the forward transverse guard fence 98.

When the guard fences have been pivoted upwardly to their working oroperative position as shown in FIG- URES 2 and 3, the sliding latches106 may be used to interlock the forward guard fence 98 with the twoside guard fences 100 and 102. In a preferred embodiment of theinvention, it is also very desirable to provide a pair of back rails107s and 107b, each of which is pivotally secured to a different one ofthe side guard fences, and which can be interlocked by means of asliding sleeve 107e.

Extending downwardly from the under side of the base frame 92 of thework platform 64, and more specifically, from each of the boom attachingbeams 92b are a pair of boom attachment brackets 108 and 110. It will benoted in referring to FIGURES 2 and 3 that each of the boom attachmentbrackets 108 is pivotally secured through a pin 111 to the inside of theupper ends of the outer boom 52. The other boom attachment brackets 110in each set are secured to the opposite side of the respective boomattaching beams 92b from the boom attaching brackets 110 and are securedby suitable pivot pins 112 to the outsides of the upper end of theinside boom 53. It will thus be noted that the staggered position of theboom connecting brackets 108 and 110 relative to each other,conjunctively with the smaller transverse dimension of the inside boom53 as compared to the outside boom 52, permit the two booms to be nestedwith the inside boom 53 positioned inside the outside boom 52 when bothbooms are lowered to a substantially horizontally extending position asshown in FIGURES 1 and 5. Moreover, the pivotal axes of the pivot pins111 and i112 extend parallel to each other, and to the axes of the pivotrods 42 and 90 used to connect the booms 52 and 53 to the base structure22 so that a parallelogram type arrangement is provided in which thebase frame 92 and floor 94 of the base platform 64 are constantlymaintained in a horizontal position as the booms 52 and 53 are pivotedupwardly. It may also be pointed out here that at such time as the innerand outer booms 53 and 52, respectively, are pivoted downwardly to theircollapsed, substantially horizontal position as shown in FIGURES 1 and5, the scaffold structure becomes locked in this position and cannot bedisplaced therefrom by vibration or tilting. Rather, a positive forcemust be applied on the outer and uppermost of the two booms in order tobreak this positive interlock and allow the parallelogram type motion tooccur.

For the purpose of elevating the booms S2 and 53 to raise the workplatform 64 to a desired height, the portable collapsible scaffold ofthe invention includes a selfcontained power plant which includes aprime mover, preferably a gasoline engine 118, which is supported on asuitable support plate 119 mounted on the base structure 22 of thescaffold. The support plate 119 also supports a hydraulic pump 122,which is driven by the engine 118 and supplies hydraulic power fluidthrough suitable conduits 124 and 126 to a main piston and cylinderassembly designated generally by reference numeral 128, and to anauxiliary piston and cylinder assembly, designated generally bereference numeral 134), respectively (see FIGURE 2). This power plant isillustrated schematically in FIGURE 9, which also depicts a pair offlo-w control valves 132 and 134 interposed between the hydraulic pump122 and the piston and cylinder assemblies 128 and 130. One of thesevalves, 132, may be termed the metering valve and controls the rate atwhich hydraulic power fluid is directed from the pump 122 into each ofthe piston and cylinder assemblies 128 and 130, or is bled from theseassemblies back to the pump 122. An operating valve is used for actuallyconnecting the pump 122 hydraulically to the piston and cylinderassemblies 128 and 130.

Referring in greater detail to the construction of the piston andcylinder assembly 128, this assembly includes an enlongated cylinder 136which is pivotally anchored by a pivot pin 138 which extends betweenanchor plates 140 secured to transverse anchor beams 142. A piston 144is located in the cylinder 136 and has secured thereto an elongatedpiston rod 146. The upper end of the piston rod 146 is pivotally securedby a pivot pin 148 to a pair of opposed bracket plates 150 secured tothe inner boom 53. The bracket plates 150 also support a transversecylinder base plate 152 (see FIGURE 3) upon which is mounted a shorthydraulic cylinder 154 which encloses a piston 155 (see FIGURE 9) havingsecured thereto, and extending from the cylinder, a relatively shortpiston rod 156 ing from the cylinder, a relatively short piston rod 156.The free upper end of the piston rod 156 bears against one of the crossmembers 60 of the boom 52 when the booms are in their collapsed, nestedrelationship as shown in FIGURES l and 5, and functions in a mannerhereinafter described for releasing the positive interlock of the boomswhich is developed when they are in their nested, horizontally extendingpositions.

For the purpose of permitting the portable collapsible scaffoldstructure 12 to be off-loaded from the vehicle 1t), there are provided aplurality of Outrigger jacks designated generally by reference numeral160, and corresponding in number to the number of the sockets 46 and 48,Each of the Outrigger jacks includes a ground-contacting plate 162 whichis secured on the lower end of a threaded shaft 164 which extendsupwardly into an internally threaded sleeve 166. A jack handle 168cooperates with the threaded shaft 164 in such a way that the shaft maybe further extended from the sleeve 166 in order to lift the basestructure 22 of the scaffolding above the bed 14 of the truck 10 in amanner hereinafter described. At its upper end, each of the Outriggerjacks 160 carries a vertically extending, socket engaging portion 170,and this portion is set horizontally inwardly from the sleeve 166 by anangulated connecting arm 172. The length and configuration of theangulated connecting arms of the outrigeer jacks are such that the lowerportions of the jacks are well clear of the sides of the vehicle 10 whenthe socket engaging portions 170 are positioned in their respectivesockets.

OPERATION Let it be assumed, for the purposes of describing theoperation of the portable collapsible scaffold of the invention, thatthe scaffold structure 12 is mounted on the bed 14 of the pickup truck1t) in the manner depicted in FIGURE 1. It will be noted that thetransverse dimensions of the base structure 22 of the scaffold permit itto easily fit between the side walls 18 of the bed of the truck, and thehorizontally extending runners 24 allow it to rest flatly and evenly onthe bed 14. The apertured securing plates 25 receive bolts which arepassed through the bed 14, and these plates are utilized for bolting thescaffold to the bed of the pickup truck by means of suitable bolts, asbest illustrated in FIGURE 8. The bolts may be quickly placed inposition, and may be self-tapping or may require the use of nuts, as maybe desired. In either event, the base structure 22 of the scaffold canbe quickly detached entirely from the bed 14 of the pickup truck so thatthe scaffold can be off-loaded from the truck in a manner hereinfaterdescribed.

With the scaffold secured on the truck in the manner depicted in FIGUREl, the truck can be driven to a location where work is to be performedon an elevated structure, such as a telephone line, light pole, traficlight, or the like. During such transport of the scaffold to thelocation of the work to be performed, the booms 52 and 53 are pivoteddownwardly to the substantially horizontal, nested position which theyare shown as occupying in FIGURE l of the drawings. In this position,the boom 53 is located inside the boom 52 and the work platform 64extends substantially horizontally and in parallelism with the booms 52and 53. In this position, a positive interlock of the booms and workplatform exists such that an upward force applied to the inner boom 53would not alone be sufficient to cause the two booms to be pivoted abouttheir respective horizontal pivotal axes. Rather, the result would be agreater binding action tending to prevent further upward movement of thebooms, since to break away from the existing interlock, the outer anduppermost boom 52 must be moved upwardly slightly before theparallelogram-typc, expanding motion can be smoothly developed.

To the end of permitting the positive interlock to be disengaged, andthe booms to pivot upwardly to the position depicted in FIGURE 2, thehydraulic piston and cylinder assemblies 128 and 130 are provided. Bothof these assemblies are actuated simultaneously by hydraulic power fluiddelivered from the pump 122. As the piston rod 146 of the main pistonand cylinder assembly 128 is extended, the short piston rod 156 of theauxiliary piston and cylinder assembly 136 is simultaneously extended sothat both of the booms 52 and 53 are simultaneously pivoted upwardlyabout their horizontal axes.

Once the interlock is disengaged by the upward movement of the upper andouter boom 52, the function of the auxiliary piston and cylinderassembly 138` is completed, and the remainder of the upward movement ofthe booms 52 and 53 can be completed by the use of the main piston andcylinder assembly 128. Accordingly, extension of the piston 146 from thecylinder 136 continues until the maximum elevation of the work platformis attained. At this time, the valve 132 is closed and the booms 52 and53 are locked in their upraised positions. The vehicle has, of course,been steered so as to position the work platform 64 in the immediatevicinity of the structure which is to be repaired, or the location wherework is to be performed by the workman.

The workman next ascends the ladder 62 which is provided on the upperside of the boom 52, using the foot supports 50 to gain access to thisladder. When the top of the ladder 62 is reached, the workman can pivotthe forward and side guard fences 98, 100 and 102 to their raisedpositions and interlock them by means of the sliding sleeve 106. Thebars 107a and 107b can be pivoted into alignment to complete theenclosure provided by the guard fences 98, 100, 102 and insure theworkmans safety as he stands upon the floor 94 and reaches outwardly toperform :repair ser-vices on any adjacent structure. It should be notedat this point that, in some instances, it may be desirable for theworkman to open the guard fences 98, 100, 102 to their operativepositions prior to the elevation of the work platform 64 `by upwardpivotation of the booms 52 and 53. This can be easily accomplished, andthe workman can stand upon the work platform 64 during the elevationthereof if this should be desired.

Upon completion of the repairs or other operations carried out by aworkman standing on the work platform 64 while it is in its elevatedposition, this platform can be lowered to the position depicted inFIGURE 1 by pivoting the booms 52 and S3 about their horizontal pivotalaxis and using the metering valve 132 to bleed hydraulic power fluidslowly out of the pistons 136 and 154. As the power fluid is dispelledfrom the cylinders, the piston rods 146 and 156 move into the respectivecylinders under the weight of the booms 52 and S3 and the work platform64. Thus, the booms 52 and 53 will gradually be lowered to theircollapsed and nested status, and the scaffold structure will again beready for transport provided, of course, that the guard fences 98, 100and 102 have been pivoted downwardly to their inoperative status asdepicted in FIG- URE 1.

In many instances, it is desirable to clear the bed 14 of the pickuptruck 10 for other uses, such as hauling various sizes and weights ofgoods and commodities from one location to another. For this to beaccomplished, it is, of course, necessary to remove the portablecollapsible scaffold 12 from the truck. This may be very quickly andeasily accomplished by a single person who may, of course, be the driverof the truck. To accomplish this, a person need merely remove the boltswhich secure the securing plates 25 to the bed 14 of the vehicle 10. TheOutrigger jacks 160 are then placed in position with each jack being setwith its socket-engaging portion 170 in one of the sockets 46 or 48.Thus, there are four jacks 160 located at the four corners of the basestructure 22 of the scaffold 12. The operator may then pass from jack tojack and by turning each of the handles 168 on the several jacks inequal relatively small incremental amounts a number of consecutivetimes, the portable collapsible scaffold can be lifted from the bed 14of the truck. If the tailgate 20 of the truck is then lowered, the truckmay simply be driven out from under the runners 24 of the base structure22 of the scaffold 12 to leave the scaffold supported in the air by thefour outrigger jacks 160i. Occasionally it may be desirable to use thescaffold while it is thus supported on the jacks 160, and this may besuccessfully accomplished due to the sufficiency of the counterbalancingWeight afforded by the base structure 22.

It should also here be noted that by slight modification of thestructure of the jacks 160 from that which is illustrated in thedrawings, the entire scaffold may be com pletely lowered to the groundby consecutively turning the handles 168 of the Outrigger jacks 160 soas to shorten the jacks until the runners 24 rest upon the ground. TheOutrigger jacks 160 may then be detached from engagement with thesockets 46 and 48 so that the portable collapsible scaffold structure 12appears as shown in FIGURE 5. In this position of the scaffoldstructure, it will be noted that the self-contained power plant, whichincludes the engine 118, the hydraulic pump 122 and the piston andcylinder assemblies 128 and 130, is still present in its same locationon the base structure 22, and can be utilized while the scaffold isrested on the ground for elevating the booms 52 and 53. Thus, thescaffold can still be employed in the location at which it is restedupon the ground for moving the work platform 64 to a relatively highvertical level to permit access to be gained to structures upon whichrepairs are to be effected.

Loading of the scaffold on the vehicle and securernent on the bedthereof is achieved in precisely the reverse manner to that in which thescaffold is off-loaded from the vehicle as hereinbefore described. Asingle person may accomplish such loading without difficulty.

Although a preferred embodiment of the portable collapsible scaffold ofthe invention has been described in order to permit its construction andoperation to be clearly understood by those having ordinary skill in theart, it is to be understood that various changes and modifications maybe made to the depicted structure without departure from the basicprinciples upon which the invention is based. All changes andmodifications of this type are therefore deemed to be circumscribed bythe spirit and scope of the invention except as the same may benecessarily limited by the appended claims or reasonable equivalentsthereof.

What is claimed is:

1. A portable, collapsible scaffold structure for mounting on aself-powered vehicle comprising:

a base structure adapted to be detachably secured to the bed of avehicle and having a forward end portion and a rear end portion;

a pair of elongated, substantially parallel boom elements each pivotallysecured at one end to the rear end portion of the base structure, saidboom elements being secured to said base structure at horizontallyspaced locations for pivotation about spaced, substantially parallel,horizontal axes;

a horizontally extending work platform pivotally secured to the ends ofsaid booms opposite their ends pivotally secured to said base structure,and forming a parallelogram with said booms and base structure when saidbooms are pivoted upwardly from said horizontally extending position;

extensible piston and cylinder element means connected between said basestructure and at least one of the booms to provide power for elevatingand lowering both booms simultaneously by pivotation about saidhorizontal axes;

means for supplying power fluid to said piston and cylinder meansmounted on said base structure;

a first plurality of sockets secured to said base structure on theopposite sides of the forward end portion thereof;

a second plurality of sockets secured to said base structure on theopposite sides of the rear end portion thereof; and

Outrigger jacks detachably engaged with said sockets, said jacks eachincluding a ground contacting lower portion and a socket entering upperportion which is horizontally offset from the lground contacting lowerportion.

2. A scaffold structure :as defined in claim 1 wherein said workplatform includes a base frame connected to said boom elements;l

floor means on the base frame; and

a plurality of guard fences pivotally attached to the side edges of saidbase frame and each pivotal from a vertically extending position to ahorizontally extending, folded down position in which said fences are inabutting contact with each other and extend parallel to each other andto said base frame.

3. A scaffold structure as defined in claim 1 and further characterizedto include multi-part pillow blocks detachably connecting said booms tosaid base structure, whereby said booms may be quickly and easilydetached from said base structure by opening said multi-part pillowblocks.

4. In combination:

a self-powered vehicle having a cab and a horizontally extending bed tothe rear of the cab;

a collapsible scaffold detachably connected to said horizontallyextending bed and including:

a base structure resting on, and detachably secured to, said bed, saidbase structure having a forward end portion adjacent said cab and a rearend portion;

a pair of elongated, substantially parallel booms each pivotally secured:at one of its ends to the rear end portion of said base structure, withsaid booms being attached to said base structure for pivotation aboutspaced, substantially parallel, horizontal pivotal axes, said boomsbeing dimensioned so that one o-f said booms will nest inside the otherboom when said booms are pivoted to a horizontally extending position ofsubstantially coplanar alignment, said booms extending over said cabwhen in said nested, horizontally extending position;

a horizontally extending work platform pivotally secured to the ends ofsaid booms opposite their ends pivotally secured to said base structure,and forming a parallelogram with said booms and base structure when saidbooms are pivoted upwardly fro-m said horizontally extending position;

means mounted on said base structure land drivingly connected to atleast one o-f said booms for simultaneously elevating said booms bypivotation about said horizontal pivotal axes;

a first pair of sockets secured to opposite sides of the forward endportion of the base structure over opposite sides of the bed of theself-powered vehicle; and

a second pair of sockets secured to the base structure on opposite sidesthereof and spaced rearwardly from said first pair of sockets.

5. The combination claimed in claim 4 wherein said booms may be pivoteddownwardly about said horizontal axes until the pivotal axes at thepoint of connection of said work platform to said booms simultaneouslypass into a common plane containing said horizontal pivotal axes wherebysaid booms are locked in said horizontally extending position.

6. The combination claimed in claim 4 and further characterized toinclude jacks slidably inserted in said sockets and extending downwardlytherefrom and to the outside of the bed of said self-powered vehicle.

7. The combination claimed in claim 4 wherein said base structureincludes two pairs of vertically extending posts; and

a multi-part pillow block at the upper end of each of said posts, thepillow blocks on each pair of said posts pivotally attaching one of saidbooms to said base structure, and said booms being detachable from saidbase structure when the parts of said pillow blocks are separated fromeach other.

8. The combination claimed in claim 4 and further characterized toinclude means mounted between said booms for biasing said booms apartfrom each other to relieve said locked status of the booms.

9. A scaffold apparatus comprising:

a base structure having a forward end portion and a rear end portion,and having a plurality of spaced, substantially horizontal runners onthe lower side thereof;

a pair of elongated, substantially parallel booms each pivotally securedat one of its ends to the rear end portion of the base structure withsaid booms being detachably connected to said base structure forpivotation about spaced, horizontal pivotal axes, said booms extendingfrom the po-ints of attachment to said base structure toward and overthe forward end portion of said base structure, and said booms differingin their transverse dimensions so that one of said booms will nestinside the other boom when said booms are pivoted to a horizontalextending position of substantially coplanar alignment;

a horizontally extending work platform pivotally secured to the ends ofsaid booms opposite their ends pivotally secured to said base structure,and forming a parallelogram with said booms and base structure when saidbooms are pivoted upwardly from said horizontally extending position;

a rst piston and cylinder assembly connected between said base structureand the one of said booms having its horizontal pivotal axis nearest theforward end portion of said base structure for pivoting said one boomupwardly upon extension of the piston rod from the cylinder of saidfirst piston and cylinder assembly;

a second piston and cylinder assembly mounted on said one boom betweenthe ends thereof and including a piston rod extendable into contact withthe other boom when said booms are in said nested, horizontallyextending position; and

means mounted on said base structure for supplying hydraulic fluid tothe cylinders of said rst and second piston and cylinder assemblies.

10. A portable, collapsible scafford structure for mounting on aself-powered vehicle comprising:

a base structure adapted to be detachably secured to the bed of avehicle and having a forward end portion and a rear end portion;

a pair of elongated, substantially parallel boom elements each pivotallysecured at one end to the rear end portion of the base structure, saidboom elements being secured to said base structure at horizontallyspaced locations for pivotation about spaced, substantially parallel,horizontal axes, one of said boom elements having its horizontal pivotalaxis forward of the horizontal pivotal axis of the other boom elementand being of lesser transverse dimensioin than said other boom element,and said boom elements being dimensioned to nest in a horizontallyextending position of substantially coplanar alignment;

a horizontally extending work platform pivotally secured to the ends ofsaid booms opposite their ends pivotally secured to said base structureand forming a parallelogram with said booms and base structure when saidbooms are pivoted upwardly from said horizontally extending position,said horizontally extending work platform occupying a position insubstantially coplanar alignment with said nested booms when said nestedbooms are in said horizontally extending position of coplanar alignment;

extensible piston and cylinder means connected between said basestructure and at least one of the booms to provide power for elevatingand lowering both booms simultaneously by pivotation about saidhorizontal axes;

means for supplying power fluid to said piston and cylinder meansmounted on said base structure; and

means connected to the forward end portion and rear end portion of saidbase structure for elevating said base structure with respect to theground to permit said self-powered vehicle to be detached and drivenfrom under said portable collapsible scatord structure.

11. A portable, collapsible scalford structure for mounting on aself-powered vehicle comprising:

a base structure adapted to be detachably secured to the bed of avehicle and having a forward end portion and a rear end portion;

a pair of elongated, substantially paraellel boom elements eachpivotally secured at one end to the rear end portion of the basestructure, said boom elements being secured to said base structure athorizontally spaced locations for pivotation about spaced, substantiallyparallel, horizontal axes;

a horizontally extending work platform pivotally secured to the ends ofsaid booms opposite their ends pivotally secured to said base structure;

extensible piston and cylinder means connected between said basestructure and at least one of the booms to provide power for elevatingand lowering both booms simultaneously by pivotation about saidReferences Cited homomal axes.; UNITED STATES PATENTS means forsupplylng power uld to said p1ston and cy1- said jacks each including aground contacting lower 3,252,542 5/1966 Thornton et 3L 182-2 lowerportion; a cylinder mounted on one of said booms; and 10 REINALDO P'MACHADO Primary Exammer a piston rod extensibly mounted in said cylinderand U Sl Cl, XR.

engageable upon extension with the other of said 182-141.63

booms for biasing said booms apart from each other. 15

